Add Json cover provider class

src/covermanager/jsoncoverprovider.h

@@ -0,0 +1,46 @@
+/*
+ * Strawberry Music Player
+ * Copyright 2018, Jonas Kvinge <jonas@jkvinge.net>
+ *
+ * Strawberry is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Strawberry is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Strawberry.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef JSONCOVERPROVIDER_H
+#define JSONCOVERPROVIDER_H
+
+#include "config.h"
+
+#include <QObject>
+#include <QByteArray>
+#include <QString>
+#include <QJsonObject>
+
+#include "coverprovider.h"
+
+class QNetworkAccessManager;
+class QNetworkReply;
+class Application;
+
+class JsonCoverProvider : public CoverProvider {
+  Q_OBJECT
+
+ public:
+  explicit JsonCoverProvider(const QString &name, const bool enabled, const bool authentication_required, const float quality, const bool fetchall, const bool allow_missing_album, Application *app, QObject *parent);
+
+  QJsonObject ExtractJsonObj(const QByteArray &data);
+
+};
+
+#endif  // JSONCOVERPROVIDER_H